Alister Doyle, writing for Reuters about a new report on the deep microbial biosphere, which may extend tens of kilometers beneath the Earth’s surface:

The single-celled microbes found deep underground include bacteria, which need water and nutrients to grow but not necessarily oxygen, and archaea, which can live off compounds such as ammonia or sulphur.

A lack of food in what the 700-page report called the “Stygian realm” – after the River Styx of the underworld in Greek mythology – meant some microbes might be “zombies”, or so slow-living as to seem dead.